The intensity observed at any pixel in an image is the result of the lighting in the photograph interacting with the color of the surface at that pixel. Explicitly uncoupling these two elements, often referred to as the reflectance and shading intrinsic images, can enable a number of image editing operations including recoloring, retexturing, and re-lighting. However, separating a single image into its reflectance and shading is a highly unconstrained problem.